Method of continuous feed of separate straps in process of blanking

ABSTRACT

The invention relates to a method of continuous feed of separate straps during the blanking, comprising the following operations: the strap of sheet material to be blanked is fed into a die, the end of the blanked strap during the movement for a feed pitch prior to the last blanking operation is deflected aside with simultaneous movement of the next strap so that the beginning of the latter overlaps the deflected end of the blanked strap, in which case the last blanking operation is effected on the blanked strap, thereafter, both straps are moved simultaneously and at the same speed for a feed pitch; at the end of this movement, prior to the first blanking operation on the next strap, the end of the blanked strap is withdrawn from the blanking zone at a speed exceeding the rate of feeding the strap into the blanking zone.

llnite Gilev et a1.

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[ 51 Mar. 2, 11972 22 Filed: Oct. 13,1969

21 Appl.No.: 872,890

[52] U.S.Cl. ..1l3/1l3 1R, 83/250,83/418,

83/446 [51] lint. C1 ..B21d 43/00 [58] Field oiSearclh ..72/338,339,420, 421,425;

References Cited 7 UNITED STATES PATENTS Primary Examiner-Richard J.l-lerbst Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT Theinvention relates to a method of continuous feed of separate strapsduring the blanking, comprising the following operations: the strap ofsheet material to be blanked is fed into a die, the end of the blankedstrap during the movement for a feed pitch prior to the last blankingoperation is deflected aside with simultaneous movement of the nextstrap so that the beginning of the latter overlaps the deflected end ofthe blanked strap, in which case the last blanking operation is effectedon the blanked strap, thereafter, both straps are moved simultaneouslyand at the same speed for a feed pitch; at the end of this movement,prior to the first blanking operation on the next strap, the end of theblanked strap is withdrawn from the blanking zone at a speed exceedingthe rate of feeding the strap into the blanking zone.

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METHOD OF CONTINUOUS FEED OF SEPARATE SlPS llN PROCESS OF BLANKINGthickness higher than 1 mm.).

Known in the art is a method of continuous feed of separate strapsduring the blanking. In this case the straps are used having differentlengths, and each strap pushed the preceding strap so that the strapsform a continuous band of the material to be blanked.

This method is suitable for blanking members of plate steel (having athickness higher than 1 mm.).

However, this method of continuous feed of separate straps by means ofpushing one strap by the other, while reducing rejection of the strapsdue to the fact that the straps form a continuous hand, does noteliminate the possibility of making rejected articles when theoverlapping joint of the straps occurs in the blanking zone. In thiscase, the more articles are blanked from one strap the less is thequantity of the rejects. In order to reduce the number of rejectedarticles, it is necessary to out off the ends of the strap, by settingthe length of the straps multiple to the pitch of feed used during themaking specific articles. This requires additional equipment and extraconsumption of time.

In addition, it should be noted that the known method has a limitedapplication and cannot be used for making of rotor and statorlaminations from sheet electrical steel, as it is rather difficult tofeed the straps of sheet steel (less than 1 mm. thick) by pushing onestrap by the other. Furthermore, when only a few stator and rotorlaminations (from 4 to 8) are punched from a single strap, theapplication of the above method to straps which are not calibrated bylength results in a high percentage of rejected articles (laminations).

Therefore, for the purposeof punching stator and rotor laminations fromsheet electrical steel, the other method of feed is employed, in whichthe use is made of calibrated straps whose length is multiple to thepitch of feed. These straps are fed to the blanking zone by means ofrollers and other driving and pulling mechanisms providing forcontinuous movement of the straps, one after another, at a constantspeed. As said above, the calibration of the straps by length requiresadditional equipment and extra consumption of time.

An object of the present invention is to provide such a method ofcontinuous feed of separate straps during the blanking, which would makeit possible to use the straps which are not calibrated by length, inparticular the straps having a positive tolerance.

This and other objects are attained due to the fact, that prior to thelast bending operation, the end of the blanked strap during the movementfor a feed pitch is bent with simultaneously movement of the next strap,the beginning of which overlaps the bent end of the blanked strap, inwhich case the last blanking operation is effected on this particularstrap, thereafter, both straps are moved simultaneously and at the samespeed for a feed pitch. At the end of this movement, prior to the firstblanking operation on the next strap, the end of the blanked strap isbeing withdrawn from the blanking zone at a speed exceeding the rate offeeding the strap to the blanking zone.

Other objects and advantages of the invention will be apparent from thefollowing description taken in connection with the accompanyingdrawings, in which:

FIG. 11 is a conventional diagrammic view of the process of blankingcircular members (stator and rotor laminations) from a strap of sheetsteel;

FIG. 2 is a diagram of bending the end of the blanked strap andoverlapping of two straps (blanked strap and the next one) prior tofeeding the next strap to the blanking zone;

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FIG. 3 is a conventional diagrammic view of the position of two strapsprior to the blanking operation on the strap and prior to feeding thenext strap to the blanking zone;

FIG. 4 shows the withdrawal of the reject of the blanked strap from theblanking zone.

The essence of the proposed method consists in the followmg.

An uncalibrated-by-length strap of sheet material (FIG. 1) devised formaking blanking members therefrom is fed into a die of an automaticpress.

By means of a mechanism 2 (FIG. 2) for feeding the strap, e.g. by meansof feeding rollers, a stick-slip motion is imparted to the strap 1. Inthis case, the strap during each stroke is displaced for a feed pitch t.

The punched members may have any prescribed shape, in particular acircular shape for stator and rotor laminations.

After the blanking, the round holes 3 remain in the strap 1 as shown inFIG. 1.

Owing to the fact that the strap 1 fed to the die is not calibrated bylength, after the blanking it has a remnant end 4 (FIG. 1) due to thepositive tolerance, the length a" of this end being less than theprescribed size of the punched member.

To provide a continuous feed of separate straps in the process ofblanking, before the last operation on the blanked strap 1, it isnecessary to set the beginning 5 (FIG. 2) of the next strap 6 to theinitial position prior to the first blanking operation on this strap,i.e. before introducing the strap 6 into the blanking zone. Thisoperation is hindered by the unsized end 4 of the blanked strap 1remaining after the last blanking operation.

According to the proposed method, the end 4 of the blanked strap 1 isbent aside by means of an attachment '7 intended for this purpose. It ismost expedient to bend this end 4 to the die 8 (FIG. 3). At the sametime the next strap 6 is moved by means of the feed rollers 2 which movethe next strap 6 at a speed V in the direction shown by the arrow A. Thenext strap 6 is set to the initial position, prior to introducing itinto the blanking zone, by compressing the spring 9 of the attachment 7.

As a result, the beginning 5 of the next strap 6 overlaps the end 4 ofthe blanked strap 1. At the same time, the last operation of the blankedstrap 1 is being effected. Due to the overlapping, the end 4 of thestrap 1 is pressed against the lifter It) and the face of the die 8, andthis makes it possible to avoid an occasional catch of the punchedmembers by the blanked strap 1.

After the last operation on the blanked strap I, both overlapped straps1 and 6 are moved simultaneously and at the same speed for a feed pitcht.

At the end of the movement, when the beginning 5 of the next strap 6moves to the initial position, as shown in FIG. 41, before effecting thefirst blanking operation on this strap, it is necessary to remove theremnant end 4 of the strap ll from the blanking zone, otherwise the diecan be broken due to the nonuniform load caused by the fact that theblanking material of a double thickness is placedat one side of the die.

In order to eliminate the breakdown of the die and to provide for theremoval of the rejects of the blanked strap during the period employedfor effecting a feed pitch, an increased rotational speed V is given tothe pull rollers Ill. In this case the blanked strap moves from theblanking zone at a speed V which exceeds the speed V Owing to this fact,the rithm of the blanking process is not disturbed, and the next blow ofthe punch 12 makes it possible to punch out a new member from the blankwhich is already on the die face.

The application of the proposed method allowed to use a strap ofelectrical steel, which is not sized by length, for blanking laminationsfor magnetic circuits of electric motors. The operation of sizing thestraps is excluded from the process of making the above-said laminationsand this increases the efficiency of the process of making thelaminations for magnetic circuits of electric motors.

What is claimed is:

fecting the final blanking operation on said first strap; simultaneouslyadvancing both straps at equal speeds through the open die zone wherebythe overlapped portions of said straps are passed therethrough; andwithdrawing the trailing edge of said first strap from said die zone ata rate of speed exceeding the rate of the movement of saidsimultaneously advanced straps.

1. A method of continuously step-feeding separate sheet material strapsin sequential order into a die for manufacturing blanks, comprising;advancing into said die a first strap to be blended; bending thetrailing edge of said strap prior to the final blanking operationthereon; simultaneously feeding a successive strap into said die towardan initial blending position, the leading edge of said successive strapoverlapping the trailing edge of said first strap when the lengththereof exceeds the multiple of the length of the feed pitch toward saiddie; effecting the final blanking operation on said first strap;simultaneously advancing both straps at equal speeds through the opendie zone whereby the overlapped portions of said straps are passedtherethrough; and withdrawing the trailing edge of said first strap fromsaid die zone at a rate of speed exceeding the rate of the movement ofsaid simultaneously advanced straps.